Surge protection systems and methods for outside plant ethernet

ABSTRACT

The present disclosure generally pertains to surge protection systems that protect outside plant equipment from high-energy surges. In one exemplary embodiment, a protection system is used for protecting Ethernet equipment that is coupled to an outside Ethernet cable. The protection system provides protection and remains capable of coupling signal energy between an Ethernet cable and Ethernet equipment without significantly degrading Ethernet performance. However, the protection system, while allowing the desirable Ethernet signals to pass between the cable and the equipment, prevents the electrical voltages and currents of high-energy surges, such as surges from lightning or AC power faults, from damaging the Ethernet equipment.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Patent ApplicationNo. 61/048,012, entitled “Surge Protection System for Outside PlantEthernet,” and filed on Apr. 25, 2008, which is incorporated herein byreference.

RELATED ART

An Ethernet interface, such as a 10/100/1000 BaseT Ethernet, hastraditionally been treated as intra-building (inside only) interfacemuch like a RS-232 interface. The Ethernet interface was not intendedfor deployment in outside plant environments where the interface may beexposed to high-energy lightning and power fault events. Safetyorganizations, such as Underwriters Laboratories (UL), and correspondingelectrical safety standards have not provided protection requirements orguidelines for Ethernet interfaces that are exposed to outside faults.As a result, placing products with inside Ethernet interface protectionto an outside environment is generally undesirable. The high-energylightning and power faults are capable of causing significant productdamage and are also electrical safety and fire hazards.

Further, from a performance standpoint, standards such as TelcordiaGR-1089-CORE, and Institute of Electrical and Electronics Engineers(I.E.E.E.) Ethernet specifications assume limited exposure to mildtransients. The mild transients typically encountered by an insideEthernet cable are induced from adjacent wiring and/or electricalequipment (e.g., motors, copiers, elevators, medical equipment, etc.).Generally, the existing protection schemes for inside Ethernetinterfaces typically comprise transient suppression circuits designed tohandle small intra-building transients. Thus, the use of Ethernet cablesand interfaces has typically been limited to indoor environments.

Recently, service providers such as Verizon, AT&T, Qwest and variousindependents, have launched initiatives that expose either the serviceprovider's Ethernet interfaces or the customer's Ethernet interfaces toan outside environment. Hence, Ethernet equipment may be damaged fromexposure to high-energy lightning (either induced or via a groundpotential rise (GPR)) or an alternating current (AC) power fault. Notonly is such an exposure a violation of one or more safety listings, butthe provider's placement of equipment may cause loss of service, damageto the equipment, and/or injury to a user.

There exist many conventional surge protection systems for protectingvarious products from high voltage and/or current surges. However, manysuch protection systems would degrade the performance of an Ethernetsignal such that the requirements of applicable Ethernet standards, suchas I.E.E.E. 802.3, would be violated. In this regard, I.E.E.E. 802.3sets limits on both the insertion loss and return loss of the Ethernetinterfaces at frequencies up to 100 mega-Hertz (MHz). Many protectionschemes, having been developed for much lower bandwidth circuits, aretherefore not suitable to Ethernet.

Moreover, there is a need for a surge protection system that protectsequipment coupled to an outside Ethernet cable. It would be desirablefor such surge protection system to be compliant with applicableEthernet transmission standards, such as I.E.E.E. 802.3.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure can be better understood with reference to the followingdrawings. The elements of the drawings are not necessarily to scalerelative to each other, emphasis instead being placed upon clearlyillustrating the principles of the disclosure. Furthermore, likereference numerals designate corresponding parts throughout the severalviews.

FIG. 1 is a block diagram illustrating an exemplary embodiment of acommunication system.

FIG. 2 is a block diagram illustrating an access multiplexer, such as isdepicted in FIG. 1, coupled to Ethernet communication equipment at acustomer premises via an Ethernet cable. The access multiplexer and theEthernet communication equipment at the customer premises are protectedby surge protection systems.

FIG. 3 is a block diagram illustrating an access multiplexer, such as isdepicted in FIG. 1, coupled to Ethernet communication equipment at acustomer premises via an Ethernet cable. The access multiplexerincorporates a surge protection system.

FIG. 4 depicts a chassis for holding surge protection systems. Thechassis is mounted on an access multiplexer, such as is depicted in FIG.2.

FIG. 5 depicts a side view of the access multiplexer and chassisdepicted by FIG. 4.

FIG. 6 depicts a chassis, such as is depicted in FIG. 4, having slotsfor receiving surge protection systems.

FIG. 7 is a side view illustrating an exemplary embodiment of a surgeprotection system to be inserted into a slot of the chassis depicted inFIG. 6.

FIG. 8 is a block diagram illustrating an exemplary embodiment of asurge protection system, such as is depicted in FIG. 2.

FIG. 9 is a circuit diagram illustrating an exemplary embodiment of avoltage limiter, such as is depicted in FIG. 8.

FIG. 10 is a circuit diagram illustrating an exemplary embodiment of avoltage limiter, such as is depicted in FIG. 8.

FIG. 11 is a circuit diagram illustrating an exemplary embodiment of avoltage limiter, such as is depicted in FIG. 8.

FIG. 12 is a block diagram illustrating an exemplary embodiment of asurge protection system, such as is depicted in FIG. 2.

FIG. 13 is a block diagram illustrating an exemplary embodiment of asurge protection system, such as is depicted in FIG. 2.

FIG. 14 is a circuit diagram illustrating an exemplary high pass filter,such as is depicted in FIG. 13.

DETAILED DESCRIPTION

The present disclosure generally pertains to surge protection systemsthat protect outside plant equipment from high-energy surges. In oneexemplary embodiment, a protection system is used for protectingEthernet equipment that is coupled to an outside Ethernet cable. Theprotection system provides protection and remains capable of couplingsignal energy between an Ethernet cable and Ethernet equipment withoutsignificantly degrading Ethernet performance. However, the protectionsystem, while allowing the desirable Ethernet signals to pass betweenthe cable and the equipment, prevents the electrical voltages andcurrents of high-energy surges, such as surges from lightning or ACpower faults, from damaging the Ethernet equipment.

FIG. 1 depicts an exemplary embodiment of a communication system 20. Thesystem 20 comprises a communication network 22. At least one networktransceiver 24 is coupled to an access multiplexer 25, such as a DigitalSubscriber Line Access Multiplexer (DSLAM), via at least onecommunication medium 27. For example, the communication medium 27 maycomprise at least one conductive connection, such as at least onetwisted pair, or at least one optical fiber. The access multiplexer 25is also coupled to a plurality of customer premises 33 via a pluralityof communication media 36. Each communication medium 36 may comprise atleast one conductive connection, such as at least one twisted pair. Inone exemplary embodiment, at least one of the communication media 36comprises an Ethernet cable, which typically has a plurality ofconductive connections bundled within a cable. For example, one type ofEthernet cable has four twisted pairs bundled within a cable, butEthernet cables with a different number of conductive connections arealso possible.

The access multiplexer 25 is configured to receive a high speed datastream from the network 22 and to demultiplex the received data acrossthe plurality of communication media 36, which often extend for shorterdistances relative to the distance of the communication medium 27.Further, the access multiplexer 25 is configured to receive data from aplurality of the customer premises 33 and to multiplex the received dataonto the communication medium 27. The use of an access multiplexer tomultiplex and demultiplex data is generally well known and will not bedescribed in detail herein for brevity purposes.

FIG. 2 depicts an exemplary embodiment in which a customer premises 33is coupled to the access multiplexer 25 via an Ethernet cable 42, suchas a category (CAT) 5 or CAT 6 cable, for example. The accessmultiplexer 25 is outside (e.g., mounted on a telephone pole), and theEthernet cable 42 runs outdoors from the customer premises 33 to theaccess multiplexer 25. The Ethernet cable 42 is, therefore, exposed tohigh voltage and/or current pulses from lightning, AC power faults,and/or other types of high energy faults. As shown by FIG. 2, one end ofthe cable 42 is coupled to a surge protection system 52, which iscoupled to Ethernet communication equipment 55 of the access multiplexer25 via an Ethernet cable 53, and the other end of the cable 42 iscoupled to a surge protection system 56, which is coupled to Ethernetcommunication equipment 59 of the customer premises 33 via an Ethernetcable 61. The surge protection system 52 protects the access multiplexer25 and, in particular, the Ethernet communication equipment 55 from highenergy surges, and the surge protection system 56 protects the Ethernetcommunication equipment 59 of the customer premises 33 from high energysurges.

In one exemplary embodiment, each surge protection system 52, 56 is astand-alone system. For example, each protection system 52, 56 may forma dongle that is detachably coupled to and, therefore, can be decoupledfrom the cable 42 and/or the Ethernet communication equipment 55, 59.Alternatively, either system 52, 56 may be integrated with the Ethernetcommunication equipment 55, 59, respectively. For example, in oneexemplary embodiment, the surge protection system 52 is integrated withthe Ethernet communication equipment 55 and housed by the accessmultiplexer housing (not shown in FIG. 2), which also houses theequipment 55. Thus, the system 52 is incorporated into the accessmultiplexer 25, as shown by FIG. 3. However, in another exemplaryembodiment, the system 55 is externally attached to the accessmultiplexer 25. Various other configurations are possible in otherembodiments.

FIGS. 4 and 5 depict an exemplary embodiment in which a chassis 63 ismounted on a housing 66 of the access multiplexer 25. The housing 66houses the Ethernet communication equipment 55 and other electricalcomponents of the access multiplexer 25. The chassis 63 has a pluralityof slots 69 (FIG. 6) into which surge protection systems 52 can berespectively inserted. As shown by FIGS. 6 and 7, each surge protectionsystem 52 has an interface panel 71, which comprises a pair of Ethernetcable connectors 74, 75. For each panel 71, one cable connector 74 iscoupled to a respective Ethernet cable 42 extending to a respectivecustomer premises 33, and the other cable connector 75 is coupled to arespective Ethernet cable 53 extending to the Ethernet communicationequipment 55 of the access multiplexer 25. Further, as shown by FIG. 7,the panel 71 is coupled to a printed circuit board (PCB) 74, referred toas “card,” on which circuitry for protecting the access multiplexer 25and, in particular, the Ethernet communication equipment 55 from highvoltage and/or current surges, as will be described in more detailhereafter.

As shown by FIG. 6, each slot 69 of the chassis 63 is associated with apair of tabs 77 having holes 79. A respective surge protection system 52is inserted into a slot 69, and the inserted system 52 is secured to thechassis 63 and, therefore, the access multiplexer 25, by inserting apair of screws 83 or other coupling devices, through the interface panel71 and the holes 79 of the associated tabs 77. In other embodiments,other configurations of the chassis 63 and surge protection system 52are possible, and other techniques may be used to secure a surgeprotection system 52 to the chassis 63 and/or access multiplexer 25.

FIG. 8 depicts an exemplary embodiment of the surge protection system 52and Ethernet communication equipment 55. Note that the surge protectionsystem 56 and the Ethernet communication equipment 59 at the customerpremises 33 may be similarly configured. In addition, for simplicity,FIG. 8 shows a pair of conductive connections 91, 92 of the Ethernetcable 42. As described above, the Ethernet cable 42 may have additionalconductive connections that are similarly arranged such that the system52 provides surge protection across all of the conductive connections ofthe Ethernet cable 42.

As shown by FIG. 8, each connection 91, 92 is coupled to a respectivefuse 101, 102. Each fuse 101, 102 is normally in a closed state suchthat electrical current is allowed to flow through the fuse 101, 102.However, when the current exceeds a threshold level, each fuse 101, 102is configured to transition to an open circuit state. Once a fuse 101,102 so transitions or, in other words, is “tripped,” the fuse can bemanually reset or replaced.

Each of the fuses 101, 102 is coupled to an isolation transformer 110,which isolates the conductive connections 91, 92 of the Ethernet cable42 from the Ethernet communication equipment 55. In this regard, theEthernet communication equipment 55 is coupled to the surge protectionsystem 52 via conductive connections 111, 112. The transformer 110 has aset of windings 116 coupled to the connections 111, 112 and a set ofwindings 117 coupled to the connections 91, 92. Energy from theconnections 91, 92 couples to the connections 111, 112 and vice versathereby allowing energy to pass through the transformer 110. Forexample, an Ethernet signal may propagate from the connections 91, 92 tothe connections 111, 112, or an Ethernet signal may propagate from theconnections 111, 112 to the connections 91, 92.

In one exemplary embodiment, the isolation transformer 110 has a highbandwidth, passing frequencies in the range from about 1 MHz to 100 MHzor more, sufficient for accommodating Ethernet signals, although otherpass-bands are possible in other embodiments. In one exemplaryembodiment, the transformer 110 has a band-pass frequency profile thatblocks frequencies below a low threshold, such as about 1 MHz, and abovea high threshold, such as about 200 MHz. In addition, the surgeprotection system 52 has low insertion loss and high return loss. Thetransformer 110 also has a high isolation voltage, such as about 5kilo-Volts (kV) or more, sufficient for protecting the Ethernetcommunication equipment 55 from high voltage surges within the surgeprotection system 52. In one exemplary embodiment, the transformer 110is constructed by using bi-filar windings to help reduce leakageinductance. In addition, the windings of the transformer 110 have heavyinsulation that is thick enough so that the transformer 110 exhibits thedesired isolation voltage, which is about 5 kV or more in one exemplaryembodiment. As a mere example, the Halo Pro-Tek5 transformer, which haspreviously been used to provide isolation of a patient from indoormedical diagnostic equipment, may be used to implement the isolationtransformer 110 of FIG. 8. The Halo Pro-Tek5 transformer is sold by HALOElectronics, Inc., 1861 Landings Drive, Mountain View, Calif. 94042.

Ethernet signals are within the pass-band of the transformer 110 and areallowed to propagate through the transformer 110 without significantdegradation. Preferably, the insertion loss is as low as possible andbelow about 1 decibel (dB) to reduce degradation of the Ethernet signaland allow a longer reach of the Ethernet cable 42. However, a higherinsertion loss is possible in other embodiments. Using the Halo Pro-Tek5transformer, the insertion loss for an Ethernet signal would be about0.1 decibel (dB) or less.

Energy from high voltage and/or current pulses can couple between thetransformer's windings 116, 117 causing high voltage and/current pulsesor “transients” to appear on the connections 111, 112 due to lightningor AC power faults. The surge protection system 52 preferably hascircuitry to sufficiently suppress such high voltage and/or currenttransients, referred to hereafter as “high energy transients,” beforethey reach the Ethernet communication equipment 55 such that damage tothe equipment 55 is prevented.

In this regard, as shown by FIG. 8, the isolation transformer 110 iscoupled to a voltage limiter 122, which is configured to suppress highenergy transients propagating on the connections 111, 112. Inparticular, the voltage limiter 122, limits the voltage potentialbetween the connections 111, 112.

FIG. 9 depicts an exemplary embodiment of the voltage limiter 122. Theexemplary voltage limiter 122 of FIG. 9 comprises a diode array of sixdiodes 141-146. The diodes 141, 142 are in series and couple theconnection 111 to the connection 112. The diodes 145, 146 are also inseries and couple the connection 111 to the connection 112. The diodes143, 144 form a bridge that couples the node between the diodes 141, 142to the node between the diodes 146, 145, as shown by FIG. 9. In oneexemplary embodiment, each diode 141-146 is an S1M diode, Adtran p/n3442S1 MS. The capacitance of the voltage limiter 122 is about 14.8pico-Farads (pF) measured between the connection 111 and the connection112. In other embodiments, other arrangements, diode types, andcapacitances are possible.

FIG. 10 depicts another exemplary embodiment of the voltage limiter 122.The embodiment of FIG. 10 is identical to the embodiment of FIG. 9except that the diode 144 of FIG. 9 is replaced by a zener diode 149 ofopposite polarity.

FIG. 11 depicts another exemplary embodiment of the voltage limiter 122.Using the same types of diodes, the voltage limiter 122 of FIG. 11 hasabout half of the capacitance and about the same transient suppressionperformance compared to the exemplary embodiment of FIG. 9, although itdoes allow about 1.5 times more voltage before limiting. This voltage isstill low enough to offer protection.

As shown by FIG. 8, the voltage limiter 122 is coupled to a transientblocking unit (TBU) 152, which is configured to suppress any high energytransients that pass through the voltage limiter 122. In one exemplaryembodiment, the transient blocking unit 152 comprises a current limiter153, as shown by FIG. 8. Other types of devices for the transientblocking unit 152 are possible in other embodiments. The transientblocking unit 152 is an added layer of protection and may be left out ofthe design if it is believed that the voltage limiter 122 is likely toprovide sufficient transient suppression.

FIG. 8 also depicts an exemplary embodiment of the Ethernetcommunication equipment 55 being protected by the surge protectionsystem 52. Other configurations are possible in other embodiments. Inthe exemplary embodiment shown by FIG. 8, the equipment 55 has atransformer 171, a diode array 172, and a processor 173 that are coupledin series to the connections 111, 112.

Capacitance generally degrades the quality of an Ethernet signalpropagating through the surge protection system 52. Thus, it isgenerally desirable to limit the capacitance of the voltage limiter 122to help keep the system 52 compliant with applicable Ethernet standards,such as I.E.E.E. 802.3 and to help maximize the reach of the Ethernetcable 42. In one exemplary embodiment, as shown by FIG. 12, at least oneinductor 161, 162 is used to compensate for the capacitance of thevoltage limiter 122. Thus, as the impedance of the voltage limiter 122drops with rising frequency, the impedance of the inductors 161, 162increases effectively canceling the change in impedance of the voltagelimiter 122 over a range of frequencies, inclusive of the expectedbandwidth of the Ethernet signal, which is about 1 MHz to about 100 MHz.Thus, the overall impedance of the surge protection system 52 remainssubstantially constant in at least the range of about 1 MHz to 100 MHz,but other ranges are possible in other embodiments.

Note that the use of the inductors 161, 162 enables the voltage limiter122 to have a higher capacitance and, therefore, larger diodes 161-166,thereby improving the array's transient suppression. Accordingly, byusing the inductors 161, 162, the system 52 is able to handle largersurges without damaging the Ethernet communication equipment 55 beingprotected by the system 52 while remaining compliant with applicableEthernet standards, such as I.E.E.E. 802.3.

In addition, the isolation transformer 110 has some leakage inductanceand the fuses 101, 102 also have some inductance. In one exemplaryembodiment, as shown by FIG. 13, at least one capacitor 166 is used inorder to compensate for the inductance of the isolation transformer 110and the fuses 101, 102. Thus, as the impedance of the transformer 110and fuses 101, 102 rises with rising frequency, the impedance of thecapacitor 166 decreases effectively canceling the change in impedance ofthe transformer 110 and fuses 101, 102 over a range of frequencies,inclusive of the expected bandwidth of the Ethernet signal.

In general, the sizes of the inductors 161, 162 and the capacitor 166are selected such that the impedance of the surge protection system 52remains substantially constant over a range of frequencies, inclusive ofthe expected bandwidth of the Ethernet signal. In one exemplaryembodiment, the impedance of the surge protection system 52 over theexpected bandwidth of the Ethernet signal substantially matches that ofthe Ethernet connections 91, 92 within the cable 42 to help increasereturn loss. Typically, such impedance is about 100 Ohms, but otherimpedances are possible. Although some tolerance in the impedancematching is acceptable, the closer that the impedance of the surgeprotection system 52 matches that of the Ethernet cable 42, the higheris the return loss. The impedance matching is sufficiently close toensure that the Ethernet signal remains compliant with applicableEthernet standards, such as I.E.E.E. 802.3.

FIG. 13 depicts an exemplary embodiment of the surge protection system52. The surge protection system 52 of FIG. 13 is similar to that of FIG.8 except that the system 52 of FIG. 13 has a high pass filter 188 inseries with the voltage limiter 122. The high pass filter 188 isconfigured to suppress energy below a certain frequency, referred to asthe “cut-off frequency.” In one exemplary embodiment, the cut-offfrequency is about 1 MHz or just below the expected bandwidth of theEthernet signal. However, other cut-off frequencies are possible inother embodiments. FIG. 14 depicts an exemplary embodiment of the highpass filter 188.

The exemplary high pass filter 188 of FIG. 14 has a capacitor 191coupled to the connection 111 and a capacitor 192 coupled to theconnection 112. In addition, the high pass filter 188 has a pair ofseries resistors 194, 195 that couple the connection 111 to theconnection 112. The node between the resistors 194, 195 is coupled toground. The capacitors 191, 192 provide a low impedance path for theEthernet signal and block lower frequencies. The resistors 194, 195 areselected to provide a desired 3 decibel break frequency, although othertypes of break frequencies may be provided in other embodiments.

The suppression provided by the high pass filter 188 reduces the totalenergy that the voltage limiter 122 must suppress to sufficientlyprotect the Ethernet equipment 55. Thus, using the high pass filter 188allows smaller diodes to be selected for the voltage limiter 122 therebyreducing the capacitance of the voltage limiter 122 and the effect ofthe voltage limiter 122 on the Ethernet signal.

Moreover, in the exemplary embodiments described above, the surgeprotection systems are capable of providing suitable surge protectionwithout significantly degrading the Ethernet signal. Thus, the Ethernetsignal remains compliant with applicable Ethernet standards, such asI.E.E.E. 802.3.

1. A communication system having a surge protection system for outsideplant Ethernet, comprising: Ethernet communication equipment configuredto transmit Ethernet signals across a first conductive connection and asecond conductive connection of an Ethernet cable extending through anoutside plant environment, the Ethernet communication equipmentconfigured to receive Ethernet signals from the first and secondconductive connections of the Ethernet cable; an isolation transformercoupled to the first and second conductive connections between theEthernet communication equipment and the Ethernet cable, the isolationtransformer having a pass-band sufficient for passing an Ethernet signalpropagating via the first and second conductive connections; at leastone fuse coupled to at least one of the first and second conductiveconnections; and a voltage limiter coupled to and positioned between theisolation transformer and the Ethernet communication equipment, thevoltage limiter configured to limit a voltage potential between thefirst and second conductive connections thereby suppressing high energytransients from the isolation transformer, wherein an isolation voltageof the transformer is sufficiently high such that a high energy powerfault occurring on the Ethernet cable is prevented from damaging theEthernet communication equipment, wherein an impedance of the surgeprotection system substantially matches an impedance of the Ethernetcable for a frequency of the Ethernet signal, and wherein thecommunication system is arranged such that the Ethernet signalstransmitted by the Ethernet communication equipment pass through thevoltage limiter, isolation transformer, and fuse and propagate acrossthe first and second conductive connections of the Ethernet cable. 2.The communication system of claim 1, wherein the Ethernet communicationequipment resides within a housing of an access multiplexer, and whereinthe Ethernet cable extends from the surge protection system to acustomer premises.
 3. The communication system of claim 1, wherein theisolation transformer, fuse, and voltage limiter are integral with theEthernet communication equipment.
 4. The communication system of claim1, wherein an insertion loss of the isolation transformer is less than 1decibel.
 5. The communication system of claim 1, wherein the isolationvoltage is at least 5,000 Volts.
 6. The communication system of claim 1,further comprising a transient blocking unit coupled to and positionedbetween the Ethernet communication equipment and the voltage limiter. 7.The communication system of claim 1, wherein the voltage limitercomprises a diode bridge.
 8. The communication system of claim 1,wherein the isolation transformer, fuse, and voltage limiter areinserted into a slot of a chassis that is mounted on an accessmultiplexer.
 9. The communication system of claim 1, further comprisingat least one capacitor for compensating for an inductance of theisolation transformer and an inductance of the fuse such that theimpedance of the isolation transformer, fuse, and voltage limiter issubstantially constant over a range of frequencies inclusive of thefrequency of the Ethernet signal, wherein the capacitor is coupled tothe voltage limiter.
 10. The communication system of claim 1, furthercomprising at least one inductor for compensating for a capacitance ofthe voltage limiter such that the total impedance of the isolationtransformer, fuse, and voltage limiter is substantially constant over arange of frequencies inclusive of the frequency of the Ethernet signal,wherein the inductor is coupled to the voltage limiter.
 11. Thecommunication system of claim 1, wherein the total impedance of theisolation transformer, fuse, and voltage limiter is about 100 Ohms. 12.The communication system of claim 1, wherein the voltage limitercomprises a diode array.
 13. The communication system of claim 12,further comprising a high pass filter coupled to the isolationtransformer and the diode array.
 14. The communication system of claim13, wherein the high pass filter is positioned between the isolationtransformer and the diode array.
 15. The communication system of claim14, wherein the diode array forms a diode bridge.
 16. A surge protectionsystem for outside plant Ethernet, comprising: an isolation transformercoupled between an Ethernet cable and Ethernet communication equipment,the isolation transformer having a pass-band sufficient for passing anEthernet signal propagating via a pair of conductive connections of theEthernet cable, wherein the Ethernet communication equipment isconfigured to transmit Ethernet signals across the pair of conductiveconnections and to receive Ethernet signals from the pair of conductiveconnections, and wherein the Ethernet cable extends through an outsideenvironment; a high pass filter coupled to the isolation transformer;and a diode array coupled to and positioned between the high pass filterand the Ethernet communication equipment, the diode array configured tolimit a voltage potential between the pair of conductive connectionsthereby suppressing high energy transients that pass through theisolation transformer and the high pass filter, wherein an isolationvoltage of the transformer is sufficiently high such that the surgeprotection system prevents a high energy power fault occurring on theEthernet cable from damaging the Ethernet communication equipment, andwherein the surge protection system is arranged such that the Ethernetsignals transmitted by the Ethernet communication equipment pass throughthe isolation transformer, high pass filter, and diode array andpropagate across the pair of conductive connections.
 17. The system ofclaim 16, wherein the Ethernet communication equipment resides within ahousing of an access multiplexer, and wherein the Ethernet cable extendsfrom the surge protection system to a customer premises.
 18. The systemof claim 16, wherein the surge protection system is integral with theEthernet communication equipment.
 19. The system of claim 16, wherein aninsertion loss of the isolation transformer is less than 1 decibel. 20.The system of claim 16, wherein the isolation voltage is at least 5,000Volts.
 21. The system of claim 16, wherein the surge protection systemis inserted into a slot of a chassis that is mounted on an accessmultiplexer.
 22. The system of claim 16, further comprising at least onecapacitor for compensating for an inductance of the isolationtransformer and an inductance of the fuse such that the impedance of thesurge protection system is substantially constant over a range offrequencies inclusive of the frequency of the Ethernet signalpropagating via the pair of conductive connections, wherein thecapacitor is coupled to the voltage limiter.
 23. The system of claim 16,further comprising at least one inductor for compensating for acapacitance of the voltage limiter such that the impedance of the surgeprotection system is substantially constant over a range of frequenciesinclusive of the frequency of the Ethernet signal propagating via thepair of conductive connections, wherein the inductor is coupled to thevoltage limiter.
 24. A communication system, comprising: a network; anaccess multiplexer coupled to the network, the access multiplexer havingEthernet communication equipment, the access multiplexer coupled to acustomer premises via an Ethernet cable extending between the accessmultiplexer and the customer premises in an outside plant environment;and a surge protection system coupled between the Ethernet cable and theEthernet communication equipment, the surge protection systemcomprising: a plurality of fuses coupled to a plurality of conductiveconnections of the Ethernet cable, the plurality of conductiveconnections including at least a first conductive connection and asecond conductive connection; an isolation transformer coupled to theplurality of fuses between the Ethernet cable and the Ethernetcommunication equipment, the isolation transformer having a pass-bandsufficient for passing an Ethernet signal propagating via the first andsecond conductive connections; a high pass filter coupled to theisolation transformer; and a voltage limiter coupled to and positionedbetween the high pass filter and the Ethernet communication equipment,the voltage limiter configured to limit a voltage potential between thefirst and second conductive connections thereby suppressing high energytransients from the high pass filter, wherein an isolation voltage ofthe transformer is sufficiently high such that the surge protectionsystem prevents a high energy power fault occurring on the Ethernetcable from damaging the Ethernet communication equipment, and wherein animpedance of the surge protection system substantially matches animpedance of the Ethernet cable for a frequency of the Ethernet signal,and wherein the surge protection system is arranged such that theEthernet signal passes through the fuses, isolation transformer, highpass filter, and voltage limiter.
 25. The system of claim 24, whereinthe voltage limiter comprises a diode array.
 26. The system of claim 25,further comprising at least one capacitor for compensating for aninductance of the isolation transformer and an inductance of the fusesuch that the impedance of the surge protection system is substantiallyconstant over a range of frequencies inclusive of the frequency of theEthernet signal, wherein the capacitor is coupled to the voltagelimiter.
 27. The system of claim 25, further comprising at least oneinductor for compensating for a capacitance of the voltage limiter suchthat the impedance of the surge protection system is substantiallyconstant over a range of frequencies inclusive of the frequency of theEthernet signal, wherein the inductor is coupled to the voltage limiter.